It might work. B&O taxes are taken out of gross income, but no where near 30%:

https://en.wikipedia.org/wiki/Business_and_occupation_tax#Ma...

So a federal B&O scheme might work if the rate was low enough. Auditing a business would be massively simplified, no need to carefully check expenses and write-offs to calculate net income. Compliance would be much easier. The question is would gross income taxation create a bigger pie, and would that pie be big enough that a low rate would substantially tax revenues.